1. Field of the Invention
The present invention relates to a portable terminal device such as a mobile phone, a personal digital assistant (PDA), etc.
2. Description of the Related Art
Conventionally, a portable terminal device represented by a mobile phone is so constructed as to, when the direction (posture) of the terminal device is changed, allow a corresponding change to be done on an array of keys (for example, Jpn. Pat. Appln. KOKAI Publication No. 2005-12493). In the portable terminal device of this KOKAI Publication, a vertical direction key matrix corresponding to key switches and character information for vertical use and a horizontal direction key matrix corresponding to key switches and character information for horizontal use are arranged. This arrangement is such that, when the horizontal posture is detected by a posture detecting section, the horizontal key matrix is read to ensure the same array as in the case where an array of numeric keys 1 to 9 is used in a vertical direction.
In a portable terminal device equipped with a display device, a structure is also shown, for example, in Jpn. Pat. Appln. KOKAI Publication No. 2000-332866,in which an information array is changed on a display device according to a posture of a terminal device.
In the conventional structure such as the portable terminal device shown in the KOKAI Publication No. 2005-12493, when the posture of the terminal device body is changed, a numeral key array is changed according to its posture and it is possible to obtain the same operability even if the terminal device is used in any direction. In this structure, however, when a posture change is detected by the sensor, the key array is automatically changed and it is so done even in the situation in which the user does not want any change in the key array. As a result, there were sometimes cases that the operability was lowered.
Further, in order not to allow the key array to be automatically changed according to a change in the posture of the terminal device, it is necessary to separately give an instruction as to whether the device should be used in a vertical posture or in a horizontal posture. In this case, each time the key array is changed, it is necessary to give a key array changing instruction to the device. This places added operational burden on the user.